Dielectrophoresis (“DEP”) refers to the force experienced by particles suspended in a fluid medium in applied electric field gradients. Due to the electric field gradient, differences in the dielectric polarization between the particles and the fluid medium cause the particles to experience a dielectrophoretic force. This effect can be quantified in terms of the electromagnetic momentum balance via the Maxwell stress tensor, or in terms of the magnitude and distribution of the charges induced on and within the particle by the applied field. Particles, such as blood cells, experiencing strong DEP motion will typically experience a DEP force of about 10−11 N, which is about 40 times greater than the gravitational settling force and about 2×105 times larger than the maximum Brownian diffusion force.
A particle's structural and physico-chemical properties can contribute towards its DEP response. This response can also depend on the frequency of the applied electric field. Due to these dependencies, variations in applied field frequencies and external environment can simultaneously probe different particle substructures and processes. For example, some fundamental electrical properties of cells, such as membrane capacitance, membrane resistance and cytoplasmic conductance affect their DEP response. These properties also reflect a cell's ability to maintain ion balances and are a measure of metabolic work and biological organization. Thus, DEP can provide a non-invasive method for determining the electrical properties of cell populations, down to the single cell level.
Accordingly, DEP has potential uses in a number of fields. For example, DEP can be used as a drug discovery tool, e.g., monitoring the dielectrophoretic response of a cell population to candidate chemical compounds. Other potential applications include separating particle populations using their differing dielectrophoretic response.